O-alkyl and alk-1-enyl lipid content of tumor cell plasma membranes are being evaluated and quantitated in relation to degree of malignancy. A comparison will be made with the ether lipid content of normal cells. Alterations in physical properties of the membranes will be examined, and the possible relation of loss of contact inhibition with ether lipid content of plasma membranes examined. Another segment of our research involves a continuation of our studies of the mechanism of ether bond formation in Ehrlich ascites tumor cells. We are currently examining certain aspects of the stereospecificity of the hydrogen exchange which we have previously reported, and which bear on the mechanism of ether bond formation.